In internal combustion engines with mechanical valve actuation, gas exchange valves are actuated by the cams of a camshaft which is driven by a crankshaft, the valve timing being definable by the arrangement and the shape of the cams. The valve timing can be selectively controlled by varying the phase relationship between the crankshaft and the camshaft as a function of the instantaneous operating state of the internal combustion engine, which makes it possible to achieve advantageous effects, such as a reduction in fuel consumption and pollutant generation.
Devices for adjusting the phase relationship between the crankshaft and the camshaft are commonly known as camshaft phasers.
In general, camshaft phasers include a drive part which is drivingly connected to the crankshaft via a drive sprocket, and an output part which is fixed to the camshaft, as well as an adjusting mechanism which is connected between the drive part and the output part and transmits the torque from the drive part to the output part and which makes it possible to adjust and fix the phase relationship between the two.
In a conventional design as a hydraulic rotary actuator, the drive part is configured as an outer rotor and the output part is configured as an inner rotor, the outer rotor and inner rotor being rotationally adjustable and arranged concentrically about a common axis of rotation. In the radial space between the outer rotor and the inner rotor, at least one hydraulic chamber is formed by one of the two rotors, and a vane connected to the respective other rotor extends into the hydraulic chamber, thereby dividing it into a pair of oppositely acting pressure chambers. By selectively pressurizing the pressure chambers, the outer rotor and the inner rotor can be adjusted relative to each other, thereby varying the phase relationship between the crankshaft and the camshaft.
For purposes of pressurizing the oppositely acting pressure chambers, the inner rotor is typically provided with holes to which a pressurized hydraulic medium can be supplied through a central opening in the inner rotor. The two hydraulic circuits must be hydraulically separated from each other by suitable sealing measures. A hydraulic camshaft phaser of this type is known, for example, from DE 10 2009 014 338, in particular FIG. 4A and FIG. 4B thereof.